Heat stores are thermal energy stores which store thermal energy (heat) and thus temporally decouple the generation of electrical energy from the generation or provision of the thermal energy. The thermal energy stored by means of the heat store can then be guided directly to the consumer as heat or can be used again for generating electrical energy.
One possible heat store is a bulk material store comprising stones or bricks as bulk material. In this case, the bulk material store is typically charged by means of a fluid at a temperature of approximately 600° C.
The prior art distinguishes between vertically and horizontally oriented heat stores. In particular, in the case of a horizontal heat store, temperature gradients, i.e. differences in temperature, can arise in various partial regions of the horizontal heat store during charging or discharging. Said undesired temperature gradients typically arise as a result of natural convection within the horizontal heat store. Said temperature gradients are disadvantageous since they lead to a non-uniform distribution of the heat during charging or discharging of the horizontal heat store. This limits the efficiency of horizontal heat stores.
According to the prior art, an attempt is made to compensate for or to prevent the temperature gradients by means of horizontal and/or vertical plates arranged within the horizontal heat store, such that an approximately uniform distribution of the temperature is established within the horizontal heat store, in particular during charging and discharging. The natural convection is hindered by means of the horizontal or vertical plates arranged in the horizontal heat store, and this consequently leads to homogenization of the temperature distribution within the horizontal heat store. A high number of plates is typically required for this purpose, however. In the case of vertically arranged plates, the pressure losses are additionally increased when charging or discharging the horizontal heat store.
A further disadvantage of known horizontal heat stores is that, in spite of the horizontally or vertically arranged plates, temperature gradients which form, for example, in phases of rest still cannot be prevented. This is therefore the case since a hot fluid, with which the horizontal heat store is charged, is arranged on the cover of the horizontal heat store, whereas the cooler or cooled fluid collects at the base of the horizontal heat store. This results in temperature gradients which lead to mechanical stresses within the heat store material, and therefore the horizontal heat store can be filled only inadequately and consequently the efficiency of the horizontal heat store is reduced.